In-situ Synthesis And Characteristics Of Polyvinyl Alcohol-hydroxyapatite Composite

Polyvinyl Alcohol hydro gel has good biocompatibility, biodegradability andespecially excellent bio tribiological properties. As it has been matched to humantissues in their properties, it can replace the cartilage tissues. Due to its poorstrength and toughness, it needs to add some inorganic particles and whiskers toimprove its mechanical properties and biology activity. Thus, in order to achieve theapplication, our research chose the hydroxyapatite mix with polyvinyl alcohol hydrogel.PVA-HA hydro gel was synthesized by in situ precipitation method，whichmeans the hydroxyapatite precipitate on the molecular of PVA. And it experiencedthe repeated freeze-thaw cycles to reach the final state. The effect of synthesismethod, the concentration ratio, the concentration of PVA and HA precursor on themicrostructure and phase were studied. Then, in vitro biological activities werecharacterized by Scanning Electron Microscope, X-Ray Diffraction, and EnergyDispersive X-ray Detector. The compression properties and swelling properties weretexted.Reducing the compression ratio can make the PVA and HA linked. When theratio is7.5%, the PVA-HA hydro gel shows the uniform microstructure. Theconcentration of inorganic salts also affects the microstructure. The more inorganicsalts we put into, the more particles porous material we get. In all, the reactants arePVA, calcium nitrate and diammonium phosphate. And the ratio of calcium nitrateand diammonium phosphate was1.67. The reaction temperature was80°C, thereaction time is about10h with2h condensation. Finally, the uniform porousPVA-HA hydro gel was achieved which experienced3freeze-thaws cycles.When the concentration of calcium nitrate was0.24mol/L, the ratio of calciumnitrate and diammonium phosphate was1.67, the mass fraction of PVA was2wt%,the PVA-HA hydro gel was attained which experienced3freeze-thaws cycles. Thesamples we got above were put into Simulated Body Fluid. After28days, thecalcium hydrogen phosphate hydroxide was deposited. In addition, adding the HA oradding the PVA can both enhance the mechanical properties and the swellingproperties. The concentration of PVA went up and the concentration of inorganicsalts went down, it could improve the swelling properties. When the concentrationof calcium nitrate was0.06mol/L, the ratio of calcium nitrate and diammoniumphosphate was1.67, the mass fraction of PVA was6wt%; the mechanical propertiesof hydro gel were better than others. When the freeze-thaw time goes up from3to9,the compression strength increased from0.41MPa to0.50MPa，about22.0%. The compression modulus fits the exponent function, which is similar to the naturecartilage. When the compression ratio of the PVA-HA hydro gel is from5%to60%，compression modulus of the PVA-HA hydro gel increased from0.07MPa to2.86MPa，about40.8time.